geo/wkt: add support for parsing polygons with Z and M dimensions

This patch extends the capabilities of the WKT parser to include
parsing of polygons with Z and M dimensions.

Release note: None

pkg/geo/wkt/lex.go

@@ -98,6 +98,14 @@ func getKeywordToken(tokStr string) int {
 		return LINESTRINGZ
 	case "LINESTRINGZM":
 		return LINESTRINGZM
+	case "POLYGON":
+		return POLYGON
+	case "POLYGONM":
+		return POLYGONM
+	case "POLYGONZ":
+		return POLYGONZ
+	case "POLYGONZM":
+		return POLYGONZM
 	default:
 		return eof
 	}

pkg/geo/wkt/wkt.y

@@ -14,25 +14,57 @@ package wkt
 
 import "github.com/twpayne/go-geom"
 
+func isValidLinestring(wktlex wktLexer, flatCoords []float64, stride int) bool {
+	if len(flatCoords) < 2 * stride {
+		wktlex.(*wktLex).Error("syntax error: non-empty linestring with only one point")
+		return false
+	}
+	return true
+}
+
+func isValidPolygonRing(wktlex wktLexer, flatCoords []float64, stride int) bool {
+	if len(flatCoords) < 4 * stride {
+		wktlex.(*wktLex).Error("syntax error: polygon ring doesn't have enough points")
+		return false
+	}
+	for i := 0; i < stride; i++ {
+		if flatCoords[i] != flatCoords[len(flatCoords)-stride+i] {
+			wktlex.(*wktLex).Error("syntax error: polygon ring not closed")
+			return false
+    }
+	}
+	return true
+}
+
+type geomPair struct {
+	flatCoords []float64
+	ends       []int
+}
+
 %}
 
 %union {
 	str       string
 	geom      geom.T
 	coord     float64
 	coordList []float64
+	pair      geomPair
 }
 
 %token <str> POINT POINTM POINTZ POINTZM
 %token <str> LINESTRING LINESTRINGM LINESTRINGZ LINESTRINGZM
+%token <str> POLYGON POLYGONM POLYGONZ POLYGONZM
 %token <str> EMPTY
-//%token <str> POLYGON MULTIPOINT MULTILINESTRING MULTIPOLYGON GEOMETRYCOLLECTION
+//%token <str> MULTIPOINT MULTILINESTRING MULTIPOLYGON GEOMETRYCOLLECTION
 %token <coord> NUM
 
 %type <geom> geometry
-%type <geom> point linestring
+%type <geom> point linestring polygon
 %type <coordList> two_coords three_coords four_coords
 %type <coordList> two_coords_list three_coords_list four_coords_list
+%type <coordList> two_coords_line three_coords_line four_coords_line
+%type <pair> two_coords_ring three_coords_ring four_coords_ring
+%type <pair> two_coords_ring_list three_coords_ring_list four_coords_ring_list
 
 %%
 
@@ -44,8 +76,8 @@ start:
 
 geometry:
 	point
-	// TODO(ayang) have parser check that linestrings are either empty or have 2+ points
 |	linestring
+|	polygon
 
 point:
 	POINT '(' two_coords ')'
@@ -90,29 +122,29 @@ point:
 	}
 
 linestring:
-	LINESTRING '(' two_coords_list ')'
+	LINESTRING two_coords_line
 	{
-		$$ = geom.NewLineStringFlat(geom.XY, $3)
+		$$ = geom.NewLineStringFlat(geom.XY, $2)
 	}
-|	LINESTRING '(' three_coords_list ')'
+|	LINESTRING three_coords_line
 	{
-		$$ = geom.NewLineStringFlat(geom.XYZ, $3)
+		$$ = geom.NewLineStringFlat(geom.XYZ, $2)
 	}
-|	LINESTRING '(' four_coords_list ')'
+|	LINESTRING four_coords_line
 	{
-		$$ = geom.NewLineStringFlat(geom.XYZM, $3)
+		$$ = geom.NewLineStringFlat(geom.XYZM, $2)
 	}
-|	LINESTRINGM '(' three_coords_list ')'
+|	LINESTRINGM three_coords_line
 	{
-		$$ = geom.NewLineStringFlat(geom.XYM, $3)
+		$$ = geom.NewLineStringFlat(geom.XYM, $2)
 	}
-|	LINESTRINGZ '(' three_coords_list ')'
+|	LINESTRINGZ three_coords_line
 	{
-		$$ = geom.NewLineStringFlat(geom.XYZ, $3)
+		$$ = geom.NewLineStringFlat(geom.XYZ, $2)
 	}
-|	LINESTRINGZM '(' four_coords_list ')'
+|	LINESTRINGZM four_coords_line
 	{
-		$$ = geom.NewLineStringFlat(geom.XYZM, $3)
+		$$ = geom.NewLineStringFlat(geom.XYZM, $2)
 	}
 |	LINESTRING EMPTY
 	{
@@ -131,6 +163,123 @@ linestring:
 		$$ = geom.NewLineString(geom.XYZM)
 	}
 
+polygon:
+	POLYGON '(' two_coords_ring_list ')'
+	{
+		$$ = geom.NewPolygonFlat(geom.XY, $3.flatCoords, $3.ends)
+	}
+|	POLYGON '(' three_coords_ring_list ')'
+	{
+		$$ = geom.NewPolygonFlat(geom.XYZ, $3.flatCoords, $3.ends)
+	}
+|	POLYGON '(' four_coords_ring_list ')'
+	{
+		$$ = geom.NewPolygonFlat(geom.XYZM, $3.flatCoords, $3.ends)
+	}
+|	POLYGONM '(' three_coords_ring_list ')'
+	{
+		$$ = geom.NewPolygonFlat(geom.XYM, $3.flatCoords, $3.ends)
+	}
+|	POLYGONZ '(' three_coords_ring_list ')'
+	{
+		$$ = geom.NewPolygonFlat(geom.XYZ, $3.flatCoords, $3.ends)
+	}
+|	POLYGONZM '(' four_coords_ring_list ')'
+	{
+		$$ = geom.NewPolygonFlat(geom.XYZM, $3.flatCoords, $3.ends)
+	}
+|	POLYGON EMPTY
+	{
+		$$ = geom.NewPolygon(geom.XY)
+	}
+|	POLYGONM EMPTY
+	{
+		$$ = geom.NewPolygon(geom.XYM)
+	}
+|	POLYGONZ EMPTY
+	{
+		$$ = geom.NewPolygon(geom.XYZ)
+	}
+|	POLYGONZM EMPTY
+	{
+		$$ = geom.NewPolygon(geom.XYZM)
+	}
+
+two_coords_ring_list:
+	two_coords_ring_list ',' two_coords_ring
+	{
+		$$ = geomPair{append($1.flatCoords, $3.flatCoords...), append($1.ends, $1.ends[len($1.ends)-1] + $3.ends[0])}
+	}
+|	two_coords_ring
+
+three_coords_ring_list:
+	three_coords_ring_list ',' three_coords_ring
+	{
+		$$ = geomPair{append($1.flatCoords, $3.flatCoords...), append($1.ends, $1.ends[len($1.ends)-1] + $3.ends[0])}
+	}
+|	three_coords_ring
+
+four_coords_ring_list:
+	four_coords_ring_list ',' four_coords_ring
+	{
+		$$ = geomPair{append($1.flatCoords, $3.flatCoords...), append($1.ends, $1.ends[len($1.ends)-1] + $3.ends[0])}
+	}
+|	four_coords_ring
+
+two_coords_ring:
+	two_coords_line
+	{
+		if !isValidPolygonRing(wktlex, $1, 2) {
+			return 1
+		}
+		$$ = geomPair{$1, []int{len($1)}}
+	}
+
+three_coords_ring:
+	three_coords_line
+	{
+		if !isValidPolygonRing(wktlex, $1, 3) {
+			return 1
+		}
+		$$ = geomPair{$1, []int{len($1)}}
+	}
+
+four_coords_ring:
+	four_coords_line
+	{
+		if !isValidPolygonRing(wktlex, $1, 4) {
+			return 1
+		}
+		$$ = geomPair{$1, []int{len($1)}}
+	}
+
+two_coords_line:
+	'(' two_coords_list ')'
+	{
+		if !isValidLinestring(wktlex, $2, 2) {
+			return 1
+		}
+		$$ = $2
+	}
+
+three_coords_line:
+	'(' three_coords_list ')'
+	{
+		if !isValidLinestring(wktlex, $2, 3) {
+			return 1
+		}
+		$$ = $2
+	}
+
+four_coords_line:
+	'(' four_coords_list ')'
+	{
+		if !isValidLinestring(wktlex, $2, 4) {
+			return 1
+		}
+		$$ = $2
+	}
+
 two_coords_list:
 	two_coords ',' two_coords_list
 	{